This weekend marks the midpoint of the program for your fall lawn, so you'll welcome the unexpected news that this could be a vacation weekend without lawn work. While you rest, others will be playing catch up. They were away on vacation in early August when the lawn program was launched; therefore, their late start has them working this weekend. For these latecomers, there is enough leeway in the schedule for you to get current by the Aug. 28-29-30 weekend. That's your target for seeding or overseeding the lawn.

Before looking ahead at lawn events for the next two weeks, let's review the past week.

On lawns where the weeds-to-grass ratio was 60-40 in late July, the evidence shows how far you've come in only two weeks. The weeds are dead, with only brown fragments of plants remaining on the lawn as reminders of what otherwise could have been a total wreck. Meanwhile, the crab grass, nutsedge, goose grass and other noxious weeds are almost dead, thanks to your second application of chemicals earlier this week. Nothing will save these weeds; by Tuesday, they will look like tombstones.

Instead of basking in your success, you'd like to clean up any loose ends. Make a careful inspection of the lawn in search of weeds that have not passed into limbo by now; if you pursue the weeds like a detective, you will probably find an isolated weed here and there holding on for dear life.

Treat these weeds this weekend with glyphosate. Add two ounces of liquid concentrate Blot-Out or Kleenup and two ounces of water to a plastic bucket. Dip an old broom into the bucket, then use the broom to apply the chemical to the weeds. One "brooming" will destroy these weeds by Wednesday.

In the coming week, adjust the rotary mower for the lowest possible cutting, secure the grass catcher and cut the lawn. Remnants of weeds will be cut to within an inch of the soil, with everything going into the bagger for transfer to trash can liners when the job is through. This probably will be your last mowing of the old lawn for four or five weeks.

As for the disaster lawn, your application of glyphosate to the lawn in the last week should have taken its toll on the weeds. If any weeds have not died off, get to them this weekend with the Blot-Out or Kleenup. However, if all weeds are dead or dying and you applied the glyphosate before last Wednesday, you can cut the lawn at your convenience. Set the wheels to provide the lowest cut, attach the grass-catcher, then scalp the lawn. Your next mowing won't take place until late September on a perfect lawn.

Now let's examine the next phase of your reconstruction program: dethatching. Thankfully, there's no deadline here. You can dethatch anytime in the next two weeks, as long as it's done before Monday, Aug. 31.

New homeowners shouldn't let this dethatching confuse them. Dethatching is nothing more than combing the lawn surface to lift debris, grass clippings, dead weeds and organic matter from the soil before you apply seed. If you seed on top of thatch, nothing will happen.

If your lawn is small, chances are you'll dethatch with a hand rake. If your lawn is huge, you'll want to rent a powered machine to make easy work of an otherwise laborious task.

Hand-raking isn't perfect, but it will do if you bear down hard on the bamboo or flexible tine steel rake. First, wear sturdy work gloves to protect your hands from blisters.

Rake for a short distance in a north-south direction, forcing the tines into the soil as you rake. You needn't worry about any good grass being dug from the soil; it won't happen. Rake the entire lawn this way, stashing everything in plastic trash can liners. Next, rake east-west to unearth more thatch. You'll need plenty of plastic bags to collect the debris.

For sprawling lawns, the rental store has an array of powered equipment. You should visit the shop long before dethatching, if just to reserve the machine for a specific day.

While many machines can dethatch a lawn, only two are worth renting: the power rake and the powered verticut machine. The power rake has stationary nail-like tines on a rotating shaft, the speed of which is governed by the throttle; the verticut machine employs specially designed blades on the shaft that comb into the soil more effectively than the tines. Unfortunately, you'll seldom find the verticut machine for rent, but you'll find the power rake. Be sure not to rent a flail mower; the soil will be a shambles if you do.

No matter which machine you rent, the tines must comb into the soil to a depth of a half-inch. Since it's unlikely that the tines or blades will be combing to this depth when you make a trial run on the lawn, you should know how to adjust the machine before you leave the rental store. Usually, a lever at the right front of the unit adjusts the depth the tines dig into the soil; you raise (unscrew) the control knob to lower the tines. Rental shops don't want you fiddling with the control, but let's face it: If the tines don't comb into the soil, there's no reason to rent the machine. Insist on knowing how to adjust the device, even if you don't use the knowledge.

Rented machines have their own history of abuse and repair. Have the manager fire up the machine so you know it works. Try to start the engine yourself at the shop.

Dethatching is relatively simple. Once you get home, make a test run of three feet on a strip of lawn, then move the machine to the side, shut down the engine and check the soil. Get down on all fours and measure the depth of the slits made by the machine on the lawn surface. Measure carefully because the success of your lawn program rests entirely on how well the debris is combed from the soil surface.

If the tines are not combing to the half-inch depth, back off on the adjusting device, fire up the engine and make another trial pass on a new strip of the lawn. Measure the depth again. Once you get to the half-inch mark, start dethatching in earnest. Run the machine around the border first, then move on to the central part of the lawn. Afterwards, redo those areas where you had the most weeds.

Now comes the most difficult part of your month-long program: getting rid of the debris raked from the surface and placed atop the grass, dead weeds or whatever on the lawn. This trash has to be removed.

To save time and energy, use the rotary mower first, with the bagging attachment in place. Adjust the wheels for the lowest possible cutting height, in effect scalping the lawn if you were really mowing. But the idea is to use the rotating blade to vacuum up as much of the debris as possible. Expect the grass-catcher to fill quickly.

Rake the residue with the bamboo rake while others bag the thatch. When you're through, dozens of trash can liners filled with debris will stand at curb side waiting for the sanitation crew.

NEXT WEEK: Grasses for sunny lawns and those for shade, grasses for luxury lawns and those tolerating foot traffic by the youngsters, seed blends you can mix yourself. Jack Eden hosts "Over the Garden Fence" on Sundays from 10 a.m. to 1 p.m. on WTOP Radio (1500 AM)